Abstract
Recently T Wave Alternans (TWA) measured on intracardiac electrograms has been shown to predict ventricular tachycardia (VT) in animal models and in patients with implantable defibrillators. We measured intracardiac bipolar electrograms (IBE) recorded in 3‐D from ischemic and normal zones in the acutely ischemic heart to predict location and mechanism of VT.Methods18 alpha chloralose anesthetized dogs were studied with 3‐D mapping after coronary artery occlusion (CAO); infarct size (IS) was measured as % of all IBE recorded which had voltage drop >45%. Mapping localized the 3‐D origin of spontaneous VT. TWA was measured on the body surface (TWA‐surf) as well as on IBE (from up to 62 anterior septal transmural sites measured by visual estimate) filtered from 3‐1300 Hz (TWA‐IBE).ResultsTWA‐surf correlated with IS in the first 30 minutes of CAO; thereafter it did not. TWA‐surf correlated with the number of IBE with TWA found in normal and ischemic sites in both epicardium and endocardium. Compared to hearts without VT the density of TWA on IBE sites was greater in hearts with VT (4.8 ± 1.7 SE vs 19.5 ± 2.6, p<0.05) Spontaneous VT tended to be focal endocardial (56%) had TWA‐IBE at the site of origin in 81%. However epicardial reentry had only 54% sites, p<0.05 vs focal, with TWA‐IBE.ConclusionTWA‐surf correlates well with TWA‐IBE. TWA‐IBE is a marker of VT regardless of mechanism. Density of TWA predicts VT.
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